Turns out the web site version of Britain's mid-market tabloid The Daily Mail is now America's third largest online newspaper, AdExchanger notes:

ComScore says MailOnline has well over 50 million monthly uniques globally and is America’s third biggest online newspaper with 19.3 million uniques behind the NYTimes.com and WashingtonPost.com.

Online advertisers salivate for inventory on MailOnline, but the company resists automated, so-called "programmatic" real-time bidding auctions for its space in favor of direct sales at premium prices.

After the Boston bombings MailOnline broke a daily traffic record with 8.9 million unique visitors.

Sean O'Neal, MailOnline's global CMO, says the Mail's own numbers can be more significant than social media: "Because our traffic is so large, within minutes of publishing a story we have a statistically significant sample and can accurately measure whether it is popular or not. ... Since our own audience sample is so significant, we do not need to look outside at social media or search to know what to optimize in either our content or our advertising programs."

If you want to target the Mail's huge audience, you're going to have to pay the Mail directly — its inventory is not for sale in online exchanges, O'Neal says: "We really consider native advertising to be a strategic solution that can't be bought via technology platforms. That's why we made so much of an investment in ramping up our American marketing force."